Various forms of video compression have been devised to compress motion video for storage and/or transmission, including various versions of the Motion Picture Experts Group (MPEG) specification promulgated by the International Organization for Standardization of Geneva, Switzerland, and the H.26x series of specifications promulgated by the International Telegraph Union (ITU) also of Geneva, Switzerland. Such forms of video compression employ a combination of lossy and lossless compression techniques that take advantage of various characteristics commonly observed in many pieces of motion video and of various limitations of the human visual system (HVS).
Among the more commonly used lossy compression techniques is quantization of blocks of coefficients of each frame of a motion video in the frequency domain to remove higher frequency components that are less perceptible to the HVS, and are therefore less likely to be missed during video playback. Such quantization has long been carried out using parameters selected to minimize distortion that is perceptible to the HVS. However, in so doing, there has long been a tendency to ignore the resulting bitcost in the resulting compressed video bitstream. As a result, target bit data rates in transmission and/or bit data sizes in storage have been repeatedly exceeded.
More recently, various rate-distortion optimization (RDO) techniques have been devised to take into account bitcosts, as well as distortion, in the performance of quantization. Unfortunately, such techniques employ more complex calculations that require considerably greater processing and/or storage resources. Such increased requirements also result in correspondingly greater electric power requirements. This can become a significant issue when such forms of video compression are performed by a portable computing device relying upon a battery for the electric power to perform such calculations. Further, such calculations have been based on the use of feedback concerning actual bitcosts of video bitstreams resulting from the video compression. Such use of feedback introduces delays in the video compression that often require still more processing and/or storage resources to overcome.